Apparatus for multiarc welding



Aug. 16, 1949. c. w. STEWARD ET AL 2,473,985

APPARATUS FOR MULTIARC WELDING Original Filed March 9, 1944 2Sheets-Sheet 1 IN VEN TORS COLBY WESTON STEWARD BY MALCOLM R. RIVENBURGH@MWZW AT TORNE Y 1949- c. w. STEWARD ET Al. 2,478,985

APPARATUS FOR MULTIARC WELDING Original Filed March 9, 1944 2Sheets-Sheet 2 Fae. 5

INVENTORS COLBY WESTON STEWARD BY MALCOLM R. RIVENBURGH ATTORNEYPatented Aug. 16, 1949 APPARATUS FOR MULTIARC WELDING Colby WestonSteward, Kenmore, and Malcolm R. Rivenburgh, Williamsville, N. Y.,assignors, by inesne assignments, to Cornell Aeronautical Laboratory,Inc., Buffalo, N. Y., a corporation of New York Original applicationMarch 9, 1944, Serial No. 525,740. Divided and this application March29, 1947, Serial No. 738,098

7 Claims. (Cl. 315-160) This application is a division of applicationSerial No. 525,740 filed March 9, 1944, now Patent No. 2,437,840.

The present invention relates to arc welding. More specifically, itrelates to the arc welding of thin metals, and is particularly suitedfor aluminum and its alloys.

The fusion welding of very thin sheet metal is diflicult, and in thecase of light alloys hitherto has been practically impossible. It isgenerally considered impractical to are weld a butt joint in aluminum oraluminum alloy sheet, when the thickness is less than A; inch. When asheet of this order of thickness is composed of 24S aluminum alloy, ithas been almost impossible to make, by existing methods, a fusion weldwhich would not crack as fast as it was welded.

It is therefore an object of this invention to provide an apparatuswhich can be employed to fusion weld aluminum and aluminum-base alloysas thin as /60 (0.016) inch without cracking. It is another object toprovide such an apparatus which can be employed to butt weld aluminumand aluminum-base alloys sheets so as to develop from 75 to 100 percentof the full strength of the sheet metal in a tension test. Other objectswill appear hereinafter.

These objects are accomplished, according to the present invention, byproviding an arc welding method wherein two or more arcs are operativeat the same time during the fusion period, and in which one of the arcsis struck between the work piece and an electrode, preferably afluxcoated or similar consumable metallic electrode, preferably with adirect current source, and another arc is struck with a carbon electrodeas at least one of its electrodes, preferably with an alternatingcurrent source.

In the drawings:

Figure l is a general schematic view of a preferred arrangement forpracticing the present invention. Figure 2 is a schematic View of a saltsolution which may be substituted for the resistance network operatingas a resistance medium in the arrangement of Figure 1. Figure 3 is ageneral schematic view of another arrangement for practicing theinvention in which two independent electric circuits are provided tosecure two arcs. Figure 4 is a general schematic view of .still anotherarrangement for practicing the invention, in which the two electriccircuits are connected through one of the carbon electrodes. Figure 5 isa general schematic view of still another arrangement for practicing theinvention, in

which the two electric circuits are connected through the work piece.

One of the arcs, in accordance with the preferred embodiment of thisinvention, is struck between two similar carbon electrodes, and may betermed a twin carbon arc, or a twin carbon torch. Conveniently, it maybe produced by means of a pair of carbon rods held at an angle to eachother. In practice, it has been found that ordinary commercial carbonwelding rods approximately 6 or 8 inches long and A; to /8 inch indiameter may be used, held at an angle of approximately 10 to 15 or moreto each other. The heat produced by the twin carbons may be varied byregulating the arc gap and also by moving the torch near to or away fromthe work. The twin carbon are or twin carbon torch may be supplied withcurrent from any suitable source, such as a commercial alternatingcurrent welding machine. Best results are obtained when alternatingcurrent is used for the twin carbon torch, although direCt current mayalso be used. Alterhating current has the advantages that equal burn-offof the carbons is provided and that symmetrical arcing from the carbonsto the work piece occurs, which would not be the case for directcurrent.

The use of the twin carbon torch has a number of advantages andfunctions. Firstly, it serves to preheat the sheet at the starting pointof welding. Secondly, the degree of heat can be controlled, as describedabove. Thirdly, the presence of the arc acts as a partially shieldedatmosphere. Fourthly, when used in combination with a metallic are ashereinafter described, it assists in supporting the metallic are,because the current used in the metallic arc circuit is, in thisprocess, too low to be maintained independently of the carbon torch.Fifthly, it helps to melt the metal and flux of the filler rod. Thesefunctions and advantages assist in securing perfect fusion while weldingaluminum and aluminum alloys.

A second arc, in accordance with the preferred embodiment of thisinvention, is struck between the work piece and any suitable metallicelectrode, preferably flux-coated, although bare electrodes may also beused. For this circuit, direct current is preferably used, and anysuitable source, such as a commercial direct current welding machine,may be employed for this purpose. The polarity for the metallic arc maybe either straight or reversed, depending upon the material to be weldedand the rod used. Reverse polarity (i. c. with the work-piece thenegative terminal) is preferably used with thin sheets, particularlywhile welding aluminum and aluminum alloys. Accurate control of thecurrent for the metallic arc is obtained by the use of a rheostat. Themetallic are may be continuous or intermittent as desired, dependingupon the manipulation of the rod.

With the use of a twin carbon arc and a metallic are, as describedabove, it is preferred to interconnect the sources of current for thesetwo arcs by means of a resistance network or analogous means. With thisarrangement, a number of additional arcs are for-med which greatly assist in the welding operation. Thus, with one of the twin carbonelectrodes connected through a resistance network to the source ofalternating current, and the metallic electrode connected throughanother portion of the same resistance network to the source of directcurrent, a number of additional arcs are obtained, which may be Iasserted through he medium of high-speed photography. One of theseadditional arcs asses from one carbon electrode to the work piece,another from the second carbon electrode to the work piece, and a thirdfrom one of the carbon electrodes to the metallic electrode. A total offive arcs is thus secured with this arran'gment.

in the preferred rerm or the invention, a twin earbohareis used *tthes'tar t to preheat the work piece, or the metallic rod, or both.During this """iotlfth e ar'cispla'ying between the carbon eleclies."The "metallic electrode and the twin 'ca'rbonelectrodes are thenbrought closer to each 8ther,'and enemy the metallic electrode isbrought so as to *be almost touching the plate. The arcs then passbetween the flux-coated electrode, the "barren-electrodes, and the work,thereby producmg the necessary Welding heat by means of ainultiplicityb'f ares.

Referring now to Figure 1 of the drawings, a hex-wate s metallic"electrode H is connected thfoughteiniihals "F3 and F4 and res'istanceele- "merit i3 of a resistance network 42 to the :positive terminal er adir'ect current welding machine 11, supplying diret'cuirent at 50 to 100'vblts. The negative terminal of the welding machine l 'l is directly"conifectedfto the work piece 8. Two carbon eieetre-ces 2% and 2 2-eenstitute a twin "carbon" 'ariliareeo'rinected to an alternatingwehihrg frhaehh e 2 B,s-upplyingalternatiiigclirreiift at 50 "to itsvolts. Elec trode a! is while e-lectrodezz-is connected thrhrrghterminals "merit be er "resistance network 4' 2. interconnechas been"attained, th'e "second "arc, "between the 'iiiik-cb'ated "electrode "11ans the work piece 1 a, is "struck, a a *the welding "operationcompleted by working the "electrodes along the .joint to be welded, asslio'wh'ih Figure 1. Durin this-operation, multiple arcs will beevolved, i. e. from the metallic electrode IE to the work piece l8 andto one of the carbon electrodes 2| and 22, from the work piece l8 toeach of the carbon electrodes 2| and and from the carbon electrodes 2|and 22 to each other. This arrangement will secure a confined, easilycontrolled heating effect necessary for joining aluminum and aluminumalloys by fusion welding.

It is obvious that the arrangement of the circuits is not limited tothat shown in Figure 1. For example, one terminal of the alternatingcurrent source may be connected to the Work "piece as well as to one ofthe carbons, producing a variable two-way action of the carbon arebetween tlie carbons or from either of the carbons to the work piece,depending upon the distance of the carbon from the work piece. An arcmay also be drawn from one of the carbons to the meallie electrode orany combination of the above. It is obvious that, with two electricalcircuits, three electrodes and the work piece, there are numerouspossible combinations.

Salt solutions, chokes or other equivalent devices, suitably arranged toproduce the same stabilizing effect and fine adjustment of current asthe resistance network l2, may be substituted iorsuch resistancenetwork. A vessel 32 containing a saline solution, for this purpose, isshown in Figure 2 of the drawings, wherein the copper plates 33, 34, 35and 36 are hung in the solution and connected to the various elementsshown in Figure 1, in place of terminals [3, -|4, l5, and 1 6,respectively, of the resistance network $2. In addition, it is obviousthat-a self-contained power 'unit maybe utilized, comprising a suitablealternating-current transformer and a copper-oxide, electronic,electrolytic, or other equivalent rectifier with resistors, chokes andreactors necessary to give good stability and fine adjustment ofcurrent.

Referring now to Figure 3, 'this illustrates a form of the invention inwhich the two electrical trode as is connected directly to the positiveter- -minal of the direct current welding machine 4.2, while the workpiece 43 is connected .directly to the negative terminal of the weldingmachine 42. The two carbon electrodes it-and 4.5 are similarly directlyconnected to the alternating current welding machine 45. In this form,there 'is considerably less control of the various :arcs than in theform shown in'Figure 1. However, the are between electrodes 44 and #5does assist insupporting the are between electrode 4| and work piece'et.The operation is similar to that'o'f the form shown in Figure 1.

In Figure 4 is shown atiorm of ithe'invention in which both directcurrent welding machine 52 and talternatingcurrent welding :machine :56are connected to one of the carbon electrodes 54. The other (negative)terminal of the "welding machine 52 is connected to the work piece -53,while the flux-coated filler :rod 5! is'nottelectr-ically connected. Thesecond .carbonelectrodee55, connected to the .weldingmachine 5E,isshorter than the electrode 54, so that one arc-is struck between theend of .electrode-.55 and the side .of electrodei't, and-the otherarcbetween electrode '54 and work piece 53. In operation, .an arc isfirst drawnbetween'thetwo carbon electrodes 54 and 55.This'pre'heats'the longcarbon'bl. "Then the latter'is touched .tothework piece '53 'so'asto draw anarc'there. From'the two arcs, suiiicientheat is developed to bring the surface of the work piece 53 and thefiller rod 5| up to welding temperature.

In the form shown in Figure 5, the two electrical circuits are connectedthrough the Work piece 63. In this form only a single carbon electrode64 is employed, connected to one terminal of the alternating currentwelding machine 66. The opposite terminal of the welding machine 66 andthe negative terminal of direct current welding machine 62 are bothconnected to the work piece 63. The positive terminal of welding machine62 is connected to a flux-coated or bare metallic rod 6i. In operation,an arc is first struck between electrode 5 8 and the work piece 63, inorder to preheat the work piece. The metallic electrode 6| is thenintroduced so as to be almost touching the work piece 53, shifting thearc to pass between the carbon electrode 64, the metallic electrode SIand the work piece 63, each arc supplementing the others.

In addition to the advantages previously mentioned, surface cleaning isnot generally necessary while welding according to the present in-Vention.

The above discussion has been in connection with several specific formsof the invention. It is obvious, however, that many changes may be madein these forms Without departing from the spirit of the invention. It isto be understood, therefore, that the invention is not to be limitedexcept as defined in the appended claims.

We claim:

1. In an arc welding apparatus, the combination of a work piece, asource of alternating current, a pair of carbon electrodes connected tosaid alternating current source whereby a heating are may be formed inproximity to the work piece, a source of direct current, a metallicwelding electrode connected to said direct current source, said directcurrent metallic electrode being movable in the atmosphere of thealternating current heating are to carry out the Welding, and thealternating current arc being movable relative to the work piece to varythe heating.

2. In an arc welding apparatus, the combination of a source ofalternating current, a pair of carbon electrodes connected to saidsource of alternating current, a source of direct current, a metallicwelding electrode connected to said source of direct current means forelectrically connecting a work piece to the direct current source toprovide a direct current welding arc between the metallic weldingelectrode and the work piece, and means for maintaining an alternatingcurrent are between the two carbon electrodes independently of thedirect current are at the metallic electrode, whereby the position ofthe metallic electrode relative to the two carbon electrodes may bevaried to facilitate the weldmg.

3. In an arc Welding apparatus, the combination of a source ofalternating current, a pair of carbon electrodes energized by saidalternating current and adapted to form a heating are, the amount ofheat being controlled by moving said are relative to an object beingwelded, a source of direct current, a metallic welding electrodeenergized by said direct current and m'oveable into and out of theatmosphere of the alternating current heating arc, whereby the directcurrent welding may be facilitated, and means for electrically connectedthe object being welded to the source of direct current to provide adirect current welding are from the metallic welding electrode to theobject being welded.

4. In an arc welding apparatus, the combination of a work piece, asource of alternating current, carbon electrodes connected to saidalternating current source, a source of direct current, a metallicwelding electrode connected to said direct current source, the carbonelectrodes being movable as a unit relative to the work piece to controlthe environment in which the welding is to be conducted, and saidmetallic direct current welding electrode being independently movablerelative to the two carbon electrodes and to the work piece, toelfectuate the welding in the favorable atmosphere created by the arc ofthe carbon electrodes.

5. In an arc welding apparatus, the combination of a source ofalternating current, a twin carbon torch energized by said alternatingcurrent to produce a heating arc, a metallic welding rod, 2. source ofdirect current energizing said metallic welding rod, and an electricalconnection to provide a direct current welding are at the work to bewelded, the current in the metallic welding circuit being too low tomaintain welding conditions independently of the said heating arc.

6. An arc welding apparatus, comprising a source of alternating current,a source of direct current, one terminal of said first source beingelectrically connected to one terminal of said second source, a firstare, a second are adjacent to said first arc, a pair of carbonelectrodes each connected through an electrical circuit to a separateterminal of said source of alternating current and constituting theelectrodes of said first arc, a work piece connected through anelectrical circuit to one terminal of said source of direct current andconstituting an electrode of said second arc, and a metallic weldin rodconnected through an electrical circuit to the other terminal of saidsource of direct current and constituting the other electrode of saidsecond arc.

7. An arc welding apparatus, comprising a source of alternating current,a source of direct current, a first arc, a second arc adjacent to saidfirst arc, a pair of carbon electrodes connected through an electricalcircuit to separate terminals of said source of alternating current andconstituting the electrodes of said first are, a work piece connectedthrough an electrical circuit to one terminal of said source of directcurrent and constituting an electrode of said second arc, a metallicwelding rod connected through an electrical circuit to the otherterminal of said source of direct current and constituting the otherelectrode of said second arc, a first resistance medium in said firstmentioned circuit connecting a terminal of said source of alternatingcurrent to one of said carbon electrodes, second resistance medium inthe circuit from the terminals of said source of direct current, and anetwork of resistance mediums connecting said first and secondresistance mediums.

COLBY WESTON STEWARD. MALCOLM R. RIVENBURGH.

No references cited.

